Year	Number
2004-01-01	19
2005-01-01	21
2006-01-01	21
2007-01-01	21
2008-01-01	21
2009-01-01	22
2010-01-01	22
2011-01-01	22
2012-01-01	23
2013-01-01	24
2014-01-01	24
2015-01-01	24
2016-01-01	25
2017-01-01	25